Magnetoresistance and Spin-Torque Ferromagnetic Resonance in Py/δPt/Al2O3 Structure

Previous studies have shown that Rashba-Edelstein effect may exist at the permalloy (Py)/Al2O3 interface due to inversion symmetry breaking. We systematically investigated the magnetoresistance and spin-torque ferromagnetic resonance (ST-FMR) in a series of Py/delta Pt/Al2O3 structures, where the Py/Al2O3 interface is decorated with or without ultra-thin Pt. The magnetoresistance measurements show that the original Py/Al2O3 exhibits an ordinary anisotropic magnetoresistance, while Pt decoration introduces an additional spin-orbit magnetoresistance. The ST-FMR measurements show that a damping-like torque does exist in Py/Al2O3 but are relatively small compared with the Pt decorated samples, and the previously observed field-like torque in Py/Al2O3 may be contributed mainly by the Oersted field caused by the current inhomogeneity. Our results suggest that the strength of spin-orbit coupling at the Py/Al2O3 interface is relatively weak and can be enhanced by Pt decoration.